The present invention relates to a switch structure, and more specifically, to a power switch with a switch contact device that is pivoted by the alloy element when the current is overloaded.
Power switches with only two states of ON and OFF functions controlled manually have been widely used in many appliances. However, it is risky to use the above power switches when the power source is unstable because overheating may occur due to overloading of the appliance and the wire easily catches fire. Some improved power switches of the prior arts include an alloy element composed of more than one metal to automatically shut off the power source when the alloy element is thermally deformed because of overheating.
For example, the power switch disclosed in U.S. Pat. No. 5,786,742, U.S. Pat. No. 5,223,813, U.S. Pat. No. 4,937,548, U.S. Pat. No. 4,661,667, U.S. Pat. No. 4,931,762, U.S. Pat. No. 5,451,729, and U.S. Pat. No. 4,704,594. In U.S. Pat. No. 4,937,548, the device includes an alloy piece, a lever, and a cam actuator. The lever is actuated by the alloy piece, and the cam actuator is used to coordinate with a seesaw actuator. Thermal deformation of the alloy piece causes the lever to move, and then the cam actuator loses support, escapes and further cuts off the power source. Overheating may occur on the alloy piece. The above power switch uses the lever, the cam actuator, and the seesaw actuator to indirectly control the conductive plate, which is used to contact with the power source. The response of the power off operation in the above power switch when overheating occurs is so slow that the overloaded current may flow into the operating appliance in a short time to damage the appliance. Additionally, the conductive plate and the alloy piece need wires to connect with each other, and the whole structure is complicated to cause the manufacturing difficulties. The alloy piece has to actuate the seesaw actuator and the lever to escape. The function of automatic power off may incorrectly operate.
Furthermore, the power switch disclosed in U. S. Pat. No. 5,786,742 uses the thermal deformation of the alloy piece to push a limited position base such that a button can automatically escape and return back. The button is used to directly contact with the contact point of the power source so that the button may conduct the overloaded current when overheating occurs. The whole structure is still complicated. In summary, those improved power switches in the prior arts can partly overcome the danger of overheating for the appliance but the response is slow and the whole structure is complicated. An advanced power switch with simpler structure and a short response time is greatly desired.
The present invention intends to provide a power switch wherein the switch contact device includes a movable member supported on a plate when the poser switch is normally used, and the movable member is pushed away from the plate by the thermally deformed alloy element due to the overloading current to shut off the circuit immediately. The present invention intends to provide a power switch wherein the switch contact device includes a movable member supported on a plate when the poser switch is normally used, and the movable member is pushed away from the plate by the thermally deformed alloy element due to the overloading current to shut off the circuit immediately.
In accordance with one aspect of the present invention, there is provided a power switch device and comprising a switch body having a switch cover body pivotably engaged with an open top of the switch body. A contact reed is biased between one end of the switch cover body and the switch body. A first contact terminal and a second contact terminal are engaged with a bottom of the switch body. A support plate and a retaining pin respectively extend from an inside of the switch body. A seat is connected to the inside of the switch body and has a first contact joint. A conductive plate has one end thereof fixedly connected to the second contact terminal and the other end of the conductive plate has a second contact joint to contact the first contact joint.
An alloy piece has one of two protrusions thereof fixedly connected to the first contact terminal and the other protrusion of the alloy piece is connected to the seat. A switch contact device is pivotably connected to the switch cover body and has a shank and a head which is located on one end of the shank. The head has a slot defined therein and the retaining pin is located in the slot. A movable member is retractably received in the shank and a first distal end of the movable member contacts the alloy piece and a second distal end movably extends from the other end of the shank. The second distal end is supported on the support plate and will be removed from the support plate to let the switch contact device be pivoted to shut off the circuit when the alloy piece is thermally deformed.
The object of the present invention is to provide a power switch device that employs a movable member biased in a pivotable switch contact device and the switch contact device is connected to the switch cover body. When the alloy piece is deformed due to the current overloading, the switch contact device is pivoted to actuate the switch cover body to open the circuit immediately.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.